This invention relates to removing bile salts from a patient.
Salts of bile acids act as detergents to solubilize and consequently aid in digestion of dietary fats. Bile acids are precursors to bile salts, and are derived from cholesterol. Following digestion, bile acids can be passively absorbed in the jejunum, or, in the case of conjugated primary bile acids, reabsorbed by active transport in the ileum. Bile acids which are not reabsorbed by active transport are deconjugated and dehydroxylated by bacterial action in the distal ileum and large intestine.
Reabsorption of bile acids from the intestine conserves lipoprotein cholesterol in the bloodstream. Conversely, blood cholesterol level can be diminished by reducing reabsorption of bile acids.
One method of reducing the amount of bile acids that are reabsorbed is oral administration of compounds that sequester the bile acids and cannot themselves be absorbed. The sequestered bile acids consequently either decompose by bacterial action or are excreted.
Many bile acid sequestrants, however, bind relatively hydrophobic bile acids more avidly than conjugated primary bile acids, such as conjugated cholic and chenodeoxycholic acids. Further, active transport in the ileum causes substantial portions of sequestered conjugated primary bile acids to be desorbed and to enter the free bile acid pool for reabsorption. In addition, the volume of sequestrants that can be ingested safely is limited. As a result, the effectiveness of sequestrants to diminish blood cholesterol levels is also limited.
Sequestering and removing bile salts (e.g., cholate, glycocholate, glycochenocholate, taurocholate, and deoxycholate salts) in a patient can be used to reduce the patient""s cholesterol level. Because the biological precursor to bile salt is cholesterol, the metabolism of cholesterol to make bile salts is accompanied by a simultaneous reduction in the cholesterol in the patient.
Cholestyramine, a polystyrene/divinylbenzene ammonium ion exchange resin, when ingested, removes bile salts via the digestive tract. This resin, however, is unpalatable, gritty and constipating. Resins which avoid (totally or partially) these disadvantages and/or possess improved bile salt sequestration properties are needed.
The invention relates to the discovery that a new class of ion exchange resins have improved bile salt sequestration properties and little to no grittiness, thereby improving the palatability of the composition.
The resins comprise cross-linked polyamines which are characterized by one or more hydrophobic substituents and, optionally, one or more quaternary ammonium containing substituents.
In general, the invention features resins and their use in removing bile salts from a patient that includes administering to the patient a therapeutically effective amount of the reaction product of:
(a) one or more crosslinked polymers, salts and copolymers thereof characterized by a repeat unit selected from the group consisting essentially of: 
where n is a positive integer and each R, independently, is H or a substituted or unsubstituted alkyl group (e.g., C1-C8 alkyl); and
(b) at least one alkylating agent. The reaction product is characterized in that: (i) at least some of the nitrogen atoms in the repeat units are unreacted with the alkylating agent; (ii) less than 10 mol % of the nitrogen atoms in the repeat units that react with the alkylating agent form quaternary ammonium units; and (iii) the reaction product is preferably non-toxic and stable once ingested.
Suitable substituents include quaternary ammonium, amine, alkylamine, dialkylamine, hydroxy, alkoxy, halogen, carboxamide, sulfonamide and carboxylic acid ester, for example.
In preferred embodiments, the polyamine of compound (a) of the reaction product is crosslinked by means of a multifunctional crosslinking agent, the agent being present in an amount from about 0.5-25% (more preferably about 2.5-20% (most preferably 1-10%)) by weight, based upon total weight or monomer plus crosslinking agent. A preferred crosslinking agent is epichlorohydrin because of its high availability and low cost. Epichlorohydrin is also advantageous because of it""s low molecular weight and hydrophilic nature, increasing the water-swellability and gel properties of the polyamine.
The invention also features compositions based upon the above-described reaction products.
The invention provides an effective treatment for removing bile salts from a patient (and thereby reducing the patient""s cholesterol level). The compositions are non-toxic and stable when ingested in therapeutically effective amounts.
Other features and advantages will be apparent from the following description of the preferred embodiments thereof and from the claims.
Compositions
Preferred reaction products include the products of one or more crosslinked polymers having the formulae set forth in the Summary of the Invention, above, and one or more alkylating agents. The polymers are crosslinked. The level of crosslinking makes the polymers completely insoluble and thus limits the activity of the alkylated reaction product to the gastrointestinal tract only. Thus, the compositions are non-systemic in their activity and will lead to reduced side-effects in the patient.
By xe2x80x9cnon-toxicxe2x80x9d it is meant that when ingested in therapeutically effective amounts neither the reaction products nor any ions released into the body upon ion exchange are harmful. Cross-linking the polymer renders the polymer substantially resistant to absorption. When the polymer is administered as a salt, the cationic counterions are preferably selected to minimize adverse effects on the patient, as is more particularly described below.
By xe2x80x9cstablexe2x80x9d it is meant that when ingested in therapeutically effective amounts the reaction products do not dissolve or otherwise decompose in vivo to form potentially harmful by-products, and remain substantially intact so that they can transport material out of the body.
By xe2x80x9csaltxe2x80x9d it is meant that the nitrogen group in the repeat unit is protonated to create a positively charged nitrogen atom associated with a negatively charged counterion.
By xe2x80x9calkylating agentxe2x80x9d it is meant a reactant which, when reacted with the crosslinked polymer, causes an alkyl group or derivative thereof (e.g., a substituted alkyl, such as an aralkyl, hydroxyalkyl, alkylammonium salt, alkylamide, or combination thereof) to be covalently bound to one or more of the nitrogen atoms of the polymer.
One example of preferred polymer is characterized by a repeat unit having the formula 
or a salt or copolymer thereof; wherein x is zero or an integer between about 1 to 4.
A second example of a preferred polymer is characterized by a repeat unit having the formula
(NHxe2x80x94CH2CH2)nxe2x80x83xe2x80x83(6)
or a salt or copolymer thereof.
A third example of a preferred polymer is characterized by a repeat unit having the formula
(NHxe2x80x94CH2CH2xe2x80x94NHxe2x80x94CH2CH2xe2x80x94NHxe2x80x94CH2CHOHxe2x80x94CH2)nxe2x80x83xe2x80x83(7)
or a salt or copolymer thereof.
The polymers are preferably crosslinked prior to alkylation. Examples of suitable crosslinking agents include acryloyl chloride, epichlorohydrin, butanedioldiglycidyl ether, ethanedioldiglycidyl ether, and dimethyl succinate. The amount of crosslinking agent is typically between 0.5 and 25 weight %, based upon combined weight of crosslinking agent and monomer, with 2.5-20%, or 1-10%, being preferred.
Typically, the amount of crosslinking agent that is reacted with the amine polymer is sufficient to cause reaction of between about 0.5 and twenty percent of the amines. In a preferred embodiment, between about 0.5 and six percent of the amine groups react with the crosslinking agent.
Crosslinking of the polymer can be achieved by reacting the polymer with a suitable crosslinking agent in an aqueous caustic solution at about 25xc2x0 C. for a period of time of about eighteen hours to thereby form a gel. The gel is then combined with water and blended to form a particulate solid. The particulate solid can then be washed with water and dried under suitable conditions, such as a temperature of about 50xc2x0 C. for a period of time of about eighteen hours.
Alkylation involves reaction between the nitrogen atoms of the polymer and the alkylating agent (which may contain additional nitrogen atoms, e.g., in the form of amido or ammonium groups). In addition, the nitrogen atoms which do react with the alkylating agent(s) resist multiple alkylation to form quaternary ammonium ions such that less than 10 mol % of the nitrogen atoms form quaternary ammonium ions at the conclusion of alkylation.
Preferred alkylating agents have the formula RX where R is a C1-C20 alkyl (preferably C4-C20), C1-C20 hydroxy-alkyl (preferably C4-C20 hydroxyalkyl), C7-C20 aralkyl, C1-C20 alkylammonium (preferably C4-C20 alkyl ammonium), or C1-C20 alkylamido (preferably C4-C20 alkyl amido) group and X includes one or more electrophilic leaving groups. By xe2x80x9celectrophilic leaving groupxe2x80x9d it is meant a group which is displaced by a nitrogen atom in the crosslinked polymer during the alkylation reaction. Examples of preferred leaving groups include halide, epoxy, tosylate, and mesylate group. In the case of, e.g., epoxy groups, the alkylation reaction causes opening of the three-membered epoxy ring.
Examples of preferred alkylating agents include a C1-C20 alkyl halide (e.g., an n-butyl halide, n-hexyl halide, n-octyl halide, n-decyl halide, n-dodecyl halide, n-tetradecyl halide, n-octadecyl halide, and combinations thereof); a C1-C20 dihaloalkane (e.g., a 1,10-dihalodecane); a C1-C20 hydroxyalkyl halide (e.g., an 11-halo-1-undecanol); a C1-C20 aralkyl halide (e.g., a benzyl halide); a C1-C20 alkyl halide ammonium salt (e.g., a (4-halobutyl) trimethylammonium salt, (6-halohexyl)trimethyl-ammonium salt, (8-halooctyl)trimethylammonium salt, (10-halodecyl)trimethylammonium salt, (12-halododecyl)-trimethylammonium salts and combinations thereof); a C1-C20 alkyl epoxy ammonium salt (e.g., a (glycidylpropyl)-trimethylammonium salt); and a C1-C20 epoxy alkylamide (e.g., an N-(2,3-eoxypropane)butyramide, N-(2,3-epoxypropane) hexanamide, and combinations thereof).
It is particularly preferred to react the polymer with at least two alkylating agents, added simultaneously or sequentially to the polymer. In one preferred example, one of the alkylating agents has the formula RX where R is a C1-C20 alkyl group and X includes one or more electrophilic leaving groups (e.g., an alkyl halide), and the other alkylating agent has the formula Rxe2x80x2X where Rxe2x80x2 is a C1-C20 alkyl ammonium group and X includes one or more electrophilic leaving groups (e.g., an alkyl halide ammonium salt).
In another preferred example, one of the alkylating agents has the formula RX where R is a C1-C20 alkyl group and X includes one or more electrophilic leaving groups (e.g., an alkyl halide), and the other alkylating agent has the formula Rxe2x80x2X where Rxe2x80x2 is a C1-C20 hydroxyalkyl group and X includes one or more electrophilic leaving groups (e.g., a hydroxy alkyl halide).
In another preferred example, one of the alkylating agents is a C1-C20 dihaloalkane and the other alkylating agent is a C1-C20 alkylammonium salt.
The reaction products may have fixed positive charges, or may have the capability of becoming charged upon ingestion at physiological pH. In the latter case, the charged ions also pick up negatively charged counterions upon ingestion that can be exchanged with bile salts. In the case of reaction products having fixed positive charges, however, the reaction product may be provided with one or more exchangeable counterions. Examples of suitable counterions include Clxe2x88x92, Brxe2x88x92, CH3OSO3xe2x88x92, HSO4xe2x88x92, SO42xe2x88x92, HCO3xe2x88x92, CO3xe2x88x92, acetate, lactate, succinate, propionate, butyrate, ascorbate, citrate, maleate, folate, an amino acid derivative, a nucleotide, a lipid, or a phospholipid. The counterions may be the same as, or different from, each other. For example, the reaction product may contain two different types of counterions, both of which are exchanged for the bile salts being removed. More than one reaction product, each having different counterions associated with the fixed charges, may be administered as well.
The alkylating agent can be added to the cross-linked polymer at a molar ratio between about 0.05:1 to 4:1, for example, the alkylating agents can be preferably selected to provide hydrophobic regions and hydrophilic regions.
The amine polymer is typically alkylated by combining the polymer with the alkylating agents in an organic solvent. The amount of first alkylating agent combined with the amine polymer is generally sufficient to cause reaction of the first alkylating agent with between about 5 and 75 of the percent of amine groups on the amine polymer that are available for reaction. The amount of second alkylating agent combined with the amine polymer and solution is generally sufficient to cause reaction of the second alkylating agent with between about 5 and about 75 of the amine groups available for reaction on the amine polymer. Examples of suitable organic solvents include methanol, ethanal, isopropanol, acetonitrile, DMF and DMSO. A preferred organic solvent is methanol.
In one embodiment, the reaction mixture is heated over a period of about forty minutes to a temperature of about 65xc2x0 C., with stirring. Typically, an aqueous sodium hydroxide solution is continuously added during the reaction period. Preferably, the reaction period at 65xc2x0 C. is about eighteen hours, followed by gradual cooling to a room temperature of about 25xc2x0 C. over a period of about four hours. The resulting reaction product is then filtered, resuspended in methanol, filtered again, and then washed with a suitable aqueous solution, such as two molar sodium chloride,and then with deionized water. The resultant solid product is then dried under suitable conditions, such as at a temperature of about 60xc2x0 C. in an air-drying oven. The dried solid can then be subsequently processed. Preferably, the solid is ground and passed through an 80 mesh sieve.
In a particularly preferred embodiment of the invention, the amine polymer is a crosslinked poly(allylamine), wherein the first substituent includes a hydrophobic decyl moiety, and the second amine substituent includes a hexyltrimethylammonium. Further, the particularly preferred crosslinked poly(allylamine) is crosslinked by epichlorohydrin that is present in a range of between about two and six percent of the amines available for reaction with the epichlorohydrin.
The invention will now be described more specifically by the examples.